The present invention relates generally to a meter for accumulating and processing electric signals and for providing an output indicative of a measured parameter, and more particularly to a programmable meter forming a part of an instrument panel for accumulating totals and rates of change in a measured parameter. Still more particularly, the present invention relates to a programmable, environmentally sealed meter used as part of an instrument panel in a measurement control center to indicate total amounts or rates of change in a measured parameter.
Totalizer and rate meters are used extensively in a variety of industries to provide a visual indication of a measured parameter. For example, totalizer and rate meters may be used on fluid flow lines in cooperation with flowmeters to indicate the total volume of fluid flowing past the flowmeter, as well as the rate of fluid flow. Typically, a totalizer/rate meter receives a series of electronic pulses generated by a source transducer, such as a flowmeter, and calculates and displays from that pulse stream the total and rate of change, expressed in the desired unit of measure.
Often, a totalizer/rate meter is exposed to a harsh and potentially destructive environment. For example, totalizer/rate meters are employed outdoors on fluid flow lines in hydrocarbon processing plants. Such meters must be encased in an environmentally sealed enclosure to prevent invasion of the various fluids to which the meters are exposed on almost a daily basis. The environmentally sealed enclosures typically are expensive to manufacture and constitute a significant portion of the cost of such meters.
From time to time, it is desirable to reprogram a totalizer/rate meter to change, for example, the units of measure displayed by the meter, the sensitivity of the meter to input signals, the frequency at which the meter display is updated, or some other feature of the meter. Reprogramming can be a significant, time-consuming problem housed within an environmentally sealed enclosure. Such meters necessarily require either an expensive, hermetically sealed connector or a certain amount of disassembly, or both, in order to gain access to the electronic or mechanical apparatus that must be altered to effect the desired changes to the operation of the meter. In addition, because the environmentally sealed enclosure must be opened, the reprogramming operation exposes the sensitive internal parts of the meter to possible environmental contamination.
Thus, it would be desirable to provide a totalizer/rate meter enclosed within a relatively inexpensive, environmentally sealed enclosure and capable of being reprogrammed rapidly, without violating the integrity of the enclosure.